Heat pipe having a composite wick structure and method for making the same

ABSTRACT

A heat pipe having a composite wick structure includes a first pipe, a second pipe, a third wick structure, a working fluid, an evaporating section, a condensing section and a transferring section. The inner wall of the first pipe is provided with a first wick structure. The evaporating section is formed on one side of the first pipe. The condensing section is formed on the other side of the first pipe. The transferring section is formed in the first pipe between the evaporating section and the condensing section. The second pipe is received in the first pipe and located in the transferring section. The outer wall of the second pipe is provided with a second wick structure. The third wick structure is provided between the first wick structure and the second wick structure. The working fluid is filled in the first pipe. By this structure, the condensed working fluid in the first pipe can quickly flow from the condensing section through the transferring section back to the evaporating section. The present invention also provides a method for making such a heat pipe.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat pipe, in particular to a heatpipe having a composite wick structure and a method for making the same.

2. Description of Prior Art

A heat-pipe type heat sink constituted of heat pipes and aheat-dissipating fin set can solve the problem relating to heatdissipation of a processor which generates more and more amount of heatrecently. Thus, such a heat-pipe type heat sink has already replaced aconventional heat sink constituted of heat-dissipating fins and a fan.However, the existing heat pipes still have problems with regard to itsheat-conducting rate and the slow reflow of an internal working fluid.Therefore, it is an important issue for the present Inventor to solvethe above-mentioned problems.

The conventional heat pipe includes a metallic pipe, a wick structureand a working fluid.

The metallic pipe has a sealed chamber. The wick structure is providedon inner walls of the metallic pipe. The working fluid is filled in thesealed chamber of the metallic pipe. An air channel is formed inside thewick structure. The wick structure serves as a liquid reflow channel. Bythis arrangement, the conventional heat pipe is obtained.

The conventional heat pipe transfers the heat by means of theliquid-vapor phase transition of the working fluid, however, the wickstructure in the conventional heat pipe is formed as only one layer.Thus, the reflow rate of the working fluid is restricted by theone-layer wick structure. Further, since the vapor-flowing direction isopposite to the liquid-reflowing direction, and the air channel isarranged adjacent to the liquid channel, the vapor-flowing rate and theliquid-reflowing rate may be negatively affected due to the interferenceoccurred in an adjoining area between the air channel and the liquidchannel. As a result, the heat-conducting performance of theconventional heat pipe cannot be enhanced further.

SUMMARY OF THE INVENTION

The present invention is to provide a heat pipe having a composite wickstructure and a method for making the same. With a multi-layer compositewick structure in a transferring section of the heat pipe, the workingfluid condensed in the condensing section of the heat pipe can quicklyflow through the transferring section back to the evaporating section.

The present invention provides a heat pipe having a composite wickstructure, including a first pipe, a second pipe, a third wickstructure, a working fluid, an evaporating section, a condensing sectionand a transferring section. A first wick structure is provided on innerwalls of the first pipe. The evaporating section is formed on one sideof the first pipe. The condensing section is formed on the other side ofthe first pipe away from the evaporating section. The transferringsection is provided in the first pipe between the evaporating sectionand the condensing section. The second pipe is received in the firstpipe and located in the transferring section. A second wick structure isformed on outer walls of the second pipe. The third wick structure isprovided between the first wick structure and the second wick structure.The working fluid is filled in the first pipe.

The present invention provides a method for making a heat pipe having acomposite wick structure, including steps of:

a) providing a first pipe having a first wick structure, narrowing andsealing one end of the first pipe;

b) providing a second pipe having a second wick structure, inserting thesecond pipe into the first pipe to form a filling space between thefirst wick structure and the second wick structure;

c) providing a third wick structure, filling the third wick structureinto the filling space;

d) providing a heating apparatus for heating the first wick structure,the second wick structure and the third wick structure to form acomposite wick structure;

e) providing a working fluid, filling the working fluid into the firstpipe; and

f) providing a degassing and soldering apparatus for degassing andsealing the first pipe.

The present invention has the following advantageous effects. The firstpipe and the second pipe are arranged to separate an air channel from aliquid channel in the transferring section. The liquid-phase workingfluid and the vapor-phase working fluid can be transferred quicklywithout any interference, thereby increasing the heat-conductingperformance of the heat pipe.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is an assembled cross-sectional view of a heat pipe of thepresent invention;

FIG. 2 is an assembled view showing that a second pipe is inserted intoa first pipe according to the present invention;

FIG. 3 is a cross-sectional view of a condensing section taken along theline 3-3 in FIG. 1;

FIG. 4 is a cross-sectional view of a transferring section taken alongthe line 4-4 in FIG. 1;

FIG. 5 is a cross-sectional view of an evaporating section taken alongthe line 5-5 in FIG. 1;

FIG. 6 is an assembled view showing that the heat pipe of the presentinvention is applied to an electronic heat-generating element;

FIG. 7 is an assembled cross-sectional view showing the heat pipe ofanother embodiment of the present invention;

FIG. 8 is a flow chart showing the method for making the heat pipe ofthe present invention;

FIG. 9 is an assembled cross-sectional view showing the heat pipe of afurther embodiment of the present invention; and

FIG. 10 is an assembled cross-sectional view showing the heat pipe of astill further embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The detailed description and technical contents of the present inventionwill become apparent with the following detailed description accompaniedwith related drawings. It is noteworthy to point out that the drawingsis provided for the illustration purpose only, but not intended forlimiting the scope of the present invention.

Please refer to FIGS. 1 to 5. The present invention provides a heat pipehaving a composite wick structure. The heat pipe 1 includes a first pipe10, a second pipe 20, a third wick structure 30 and a working fluid 40.

Please refer to FIG. 2 first. The first pipe 10 is made of metal havinggood thermal conductivity, such as copper. The inner walls of the firstpipe 10 are provided with a plurality of grooves 11 arranged atintervals in parallel to an axial line of the first pipe 10. Each of thegrooves 11 is configured to extend through the front and rear ends ofthe first pipe 10. These grooves 11 form the first wick structure 12 ofthe present embodiment, but it is not limited thereto.

The second pipe 20 is also made of metal having good thermalconductivity, such as copper. Outer walls of the second pipe 20 areprovided with a plurality of grooves 21 arranged at intervals inparallel to an axial line of the second pipe 20. Each of the grooves 21is configured to extend through the front and rear ends of the secondpipe 20. These grooves 21 form the second wick structure 22 of thepresent embodiment, but it is not limited thereto. On the other hand,the inner wall surface of the second pipe is a smooth surface 23. Thelength and diameter of the second pipe 20 are both smaller than those ofthe first pipe 10, so that the second pipe 20 can be received in amiddle portion of the first pipe 10. The grooves 21 of the second pipe20 may be aligned with the grooves 11 of the first pipe 10 respectivelyas shown in FIG. 4. Alternatively, the grooves 21 of the second pipe 20may be staggered with respect to the grooves 11 of the first pipe 10respectively as shown in FIG. 10. The second wick structure 22 may bemade of sintered metal powder or metallic woven meshes (not shown).

The third wick structure 30 of the present embodiment is made ofsintered metal powder, but it is not limited thereto. The third wickstructure 30 is filled in the first pipe 10, and a portion of the thirdwick structure 30 is located between the first wick structure 12 and thesecond wick structure 22. By this arrangement, the second pipe 20 can befirmly supported and position in the first pipe 10.

The working fluid 40 may be pure water, which is filled in the firstpipe 10. After the interior of the first pipe 10 is degassed to becomevacuum, the first pipe 10 is sealed to obtain a desired heat pipe 1.

According to the thermal contact location in practice use, the heat pipe1 can be divided into an evaporating section 100, a condensing section101 and a transferring section 102 as shown in FIG. 1. The evaporatingsection 100 is brought into thermal contact with a heat source 6 asshown in FIG. 6. The condensing section 101 is brought into thermalcontact with a heat-dissipating fin set 7 as shown in FIG. 6 and islocated away from the evaporating section 100. The transferring section102 is located between the evaporating section 100 and the condensingsection 101. In the present embodiment, the second pipe 20 is located inthe transferring section 102 of the heat pipe 1. In the transferringsection 102, the first wick structure 12, the second wick structure 22and the third wick structure 30 constitute a three-layer composite wickstructure.

Please refer to FIG. 6. The heat pipe 1 of the present invention can becombined with the heat-dissipating fin set 7 for dissipating the heatgenerated by an electronic heat-generating source 6 (such as aprocessing chip) on a mother board. The evaporating section 100 of theheat pipe 1 is adhered to a heat-generating surface of the electronicheat-generating source 6, so that the heat generated by the electronicheat-generating source 6 can be absorbed by the evaporating section 100.As a result, the liquid-phase working fluid 40 in the evaporatingsection 100 is heated to become a vapor-phase working fluid 40. Thevapor-phase working fluid 40 flows through the second pipe 20 in thetransferring section 102. The smooth surface 23 inside the second pipe20 has a smaller flow resistance, so that the vapor-phase working liquid40 can pass through the second pipe 20 quickly and then arrive thecondensing section 101 in the first pipe 10. With the heat-dissipatingfin set 7 connected to the condensing section 101, the latent heat ofthe vapor-phase working fluid 40 can be released and dissipated to theoutside, whereby the vapor-phase working fluid 40 is condensed into aliquid-phase working fluid 40. The working fluid 40 condensed in thecondensing section 101 flows back to the transferring section 102 bymeans of a capillary force generated by the first wick structure 12 andthe third wick structure 30. Then, the condensed working fluid 40 flowsfrom the transferring section 102 back to the evaporating section 100 bymeans of a larger capillary force generated by the composite wickstructure constituted of the first wick structure 12, the second wickstructure 22 and the third wick structure 30. In this way, the workingfluid 40 can be continuously circulated in the heat pipe 1.

Please refer to FIG. 7. In addition to the above embodiment, the presentinvention can be carried out in another aspect, in which only the firstwick structure 12 is formed in the condensing section 101 of the heatpipe V. Due to its small thermal resistance, the first wick structure 12can accelerate the flowing rate of the working fluid 40 in the heat pipeV.

Please refer to FIGS. 1 and 8. The present invention provides a methodfor making a heat pipe having a composite wick structure, which includessteps of:

a) providing a first pipe 10 having a first wick structure 12, narrowingand sealing one end of the first pipe 10;

b) providing a second pipe 20 having a second wick structure 22,inserting the second pipe 20 into the first pipe 10 to form a fillingspace between the first wick structure 12 and the second wick structure22;

c) providing a third wick structure 30, filling the third wick structure30 into the filling space;

d) providing a heating apparatus for heating the first wick structure12, the second wick structure 22 and the third wick structure 30 to forma composite wick structure;

e) providing a working fluid 40, filling the working fluid 40 into thefirst pipe 10; and

f) providing a degassing and soldering apparatus for degassing andsealing the first pipe 10.

More specifically, in the present embodiment, if the third wickstructure 30 is made of sintered metal powder, a core rod (not shown)has to be inserted into the second pipe 20 first. Then, as shown in FIG.2, the second pipe 20 together with the core rod are inserted into thefirst pipe 10, thereby forming a filling space between the first wickstructure 12 and the second wick structure 22. Thereafter, metal powderis filled in the filling space. Then, a heating apparatus (not shown) isused to sinter the metal powder to form a composite wick structureconstituted of the first wick structure 12, the second wick structure 22and the third wick structure 30 made of sintered metal powder.

As shown in FIG. 5, in the evaporating section 100, a solid body isformed by the first wick structure 12 constituted of the grooves 11 andthe third wick structure 30 made by sintered metal powder. As shown inFIG. 3, in the condensing section 101, a hollow body is formed by thefirst wick structure 12 constituted of the grooves 11 and the third wickstructure 30 made of sintered metal powder.

Please refer to FIGS. 9 and 10. In addition to the above embodiment, thethird wick structure 30 of the present invention may be made by metallicwoven meshes shown in FIG. 9 or a bundle of fibers shown in FIG. 10.

Although the present invention has been described with reference to theforegoing preferred embodiments, it will be understood that theinvention is not limited to the details thereof. Various equivalentvariations and modifications can still occur to those skilled in thisart in view of the teachings of the present invention. Thus, all suchvariations and equivalent modifications are also embraced within thescope of the invention as defined in the appended claims.

1. A heat pipe having a composite wick structure, including: a firstpipe provided with a first wick structure on its inner wall; anevaporating section formed on one side of the first pipe; a condensingsection formed on the other side of the first pipe away from theevaporating section; a transferring section formed in the first pipebetween the evaporating section and the condensing section; a secondpipe received in the first pipe and located in the transferring section,an outer wall of the second pipe being provided with a second wickstructure; a third wick structure provided between the first wickstructure and the second wick structure; and a working fluid filled inthe first pipe.
 2. The heat pipe having a composite wick structureaccording to claim 1, wherein the first wick structure is constituted ofa plurality of grooves formed on the inner wall of the first pipe. 3.The heat pipe having a composite wick structure according to claim 2,wherein the second wick structure is constituted of a plurality ofgrooves formed on the outer wall of the second pipe.
 4. The heat pipehaving a composite wick structure according to claim 3, wherein thegrooves of the first pipe are aligned with the grooves of the secondpipe respectively.
 5. The heat pipe having a composite wick structureaccording to claim 3, wherein the grooves of the first pipe arestaggered with respect to the grooves of the second pipe respectively.6. The heat pipe having a composite wick structure according to claim 1,wherein the second wick structure is made of sintered metal powder. 7.The heat pipe having a composite wick structure according to claim 1,wherein the second wick structure is made of metallic woven meshes. 8.The heat pipe having a composite wick structure according to claim 1,wherein the third wick structure is made of sintered metal powder. 9.The heat pipe having a composite wick structure according to claim 1,wherein the third wick structure is made of metallic woven meshes. 10.The heat pipe having a composite wick structure according to claim 1,wherein the third wick structure is made of a bundle of fibers.
 11. Theheat pipe having a composite wick structure according to claim 1,wherein an inner wall surface of the second pipe is a smooth surface.12. The heat pipe having a composite wick structure according to claim1, wherein a solid body is formed in the evaporating section, the solidbody is constituted of the first wick structure and the third wickstructure.
 13. The heat pipe having a composite wick structure accordingto claim 1, wherein a hollow body is formed in the condensing section,the hollow body is constituted of the first wick structure and the thirdwick structure.
 14. The heat pipe having a composite wick structureaccording to claim 1, wherein the interior of the condensing section hasthe first wick structure.
 15. A method for making a heat pipe having acomposite wick structure, including steps of: a) providing a first pipehaving a first wick structure, narrowing and sealing one end of thefirst pipe; b) providing a second pipe having a second wick structure,inserting the second pipe into the first pipe to form a filling spacebetween the first wick structure and the second wick structure; c)providing a third wick structure, filling the third wick structure intothe filling space; d) providing a heating apparatus for heating thefirst wick structure, the second wick structure and the third wickstructure to form a composite wick structure; e) providing a workingfluid, filling the working fluid into the first pipe; and f) providing adegassing and soldering apparatus for degassing and sealing the firstpipe.
 16. The method according to claim 15, wherein the first wickstructure is formed of a plurality of grooves on an inner wall of thefirst pipe.
 17. The method according to claim 16, wherein the secondwick structure is constituted of a plurality of grooves on an outer wallof the second pipe.
 18. The method according to claim 17, wherein thegrooves of the first pipe are aligned with the grooves of the secondpipe respectively.
 19. The method according to claim 17, wherein thegrooves of the first pipe are staggered with respect to the grooves ofthe second pipe respectively.